1. Field of the Invention
The present invention relates to a printing apparatus, a fusing apparatus, and a method of controlling a fusing temperature of the printing apparatus. More particularly, the present invention relates to a printing apparatus comprising a heat roller including a first heat source and a second heat source with a lower heat capacity than the first heat source to fuse a toner image formed on a printing medium, a fusing apparatus, and a method of controlling a fusing temperature of the printing apparatus.
2. Description of the Related Art
In general, electrophotographic printing apparatuses, such as printers or digital multi-function machines, include fusing apparatuses that fuse a toner image formed on a printing medium. These digital multi-function machines are designed to offer at least one of the features of a printer, scanner, copier, and facsimile.
A conventional fusing apparatus employing a halogen lamp is disclosed in U.S. Patent Publication No. 2002-136562, the entire disclosure of which is hereby incorporated by reference.
FIG. 1 is a schematic diagram of a conventional fusing apparatus including a heat roller and a pressure roller. Referring to FIG. 1, a fusing apparatus 10 includes a cylindrical heat roller 11 and a pressure roller 13 disposed under the heat roller 11 to face the heat roller 11. A printing medium 14 is placed between the heat roller 11 and the pressure roller 13.
A halogen lamp 12 is installed as a heat source in the center of the heat roller 11. A coating layer 11a made of Teflon is formed on a surface of the heat roller 11. The halogen lamp 12 inside the heat roller 11 generates heat, and the heat roller 11 is heated by radiant heat transferred from the halogen lamp.
The pressure roller 13 is elastically supported by a spring unit 13a such that the pressure roller 13 presses the printing medium 14 passing between the heat roller 11 and the pressure roller 14 toward the heat roller 11 under a predetermined pressure. While passing between the heat roller 11 and the pressure roller 13, a powder toner image 14a formed on the printing medium 14 is pressed and heated by a predetermined pressure and heat. That is, the toner image 14a is fused and fixed to the printing medium 14 due to the predetermined heat and pressure generated by the heat roller 11 and the pressure roller 13.
The conventional fusing apparatus having a single heat source inside the heat roller, however, requires a considerably long warm-up time until the heat roller reaches a fusing temperature after the apparatus is turned on to perform a printing operation. Further, if the warm-up time is reduced incorrectly, a high temperature overshoot occurs. In addition, when a single halogen lamp is used, it is difficult for a high speed printer, such as those operating at about 50 ppm, to ensure a stable fusing operation during continuous printing, and power consumption is high.
Accordingly, a need exists for a system and method to efficiently perform a heat roller warm-up having a reduced warm-up time and minimal temperature overshoot.